Use LINQ XDocument

Parser/Elements/Context.cs

@@ -1,12 +1,11 @@
-using System.Xml;
+using System.Xml.Linq;
 
 namespace XNeedle.Parser.Elements
 {
     public class Context
     {
         public string? XPathSelector { get; set; }
-        public XmlNodeList? Nodes { get; set; }
+        public XElement? Node { get; set; }
-        public XmlNode? Node { get; set; }
 
         public Context Clone()
         {

Program.cs

@@ -35,15 +35,35 @@ namespace XNeedle
         static void RunOptions(Options opts)
         {
             var masterRule = (Rule)XnParser.RuleObject.Parse(File.ReadAllText(opts.XnDefinition));
-            var doc = new XmlDocument();
+            var doc = XDocument.Load(opts.Input, LoadOptions.PreserveWhitespace);
-            doc.PreserveWhitespace = true;
-            doc.Load(opts.Input);
             masterRule.Transform(doc);
-            doc.Save(opts.Output);
+            doc.Save(opts.Output, SaveOptions.DisableFormatting);
             
             Console.WriteLine($"Applied \"{opts.XnDefinition}\" to \"{opts.Input}\" and saved result to \"{opts.Output}\"");
         }
 
         static void HandleParseError(IEnumerable<Error> errs) {}
     }
+
+    public static class DocumentExtensions
+    {
+        public static XmlDocument ToXmlDocument(this XDocument xDocument)
+        {
+            var xmlDocument = new XmlDocument();
+            using(var xmlReader = xDocument.CreateReader())
+            {
+                xmlDocument.Load(xmlReader);
+            }
+            return xmlDocument;
+        }
+
+        public static XDocument ToXDocument(this XmlDocument xmlDocument)
+        {
+            using (var nodeReader = new XmlNodeReader(xmlDocument))
+            {
+                nodeReader.MoveToContent();
+                return XDocument.Load(nodeReader);
+            }
+        }
+    }
 }

Transformation/ContextFunctions.cs

@@ -33,88 +33,43 @@ namespace XNeedle.Transformation
             }
             int crc = 0xAFFE;
 
-            XmlWriterSettings settings = new XmlWriterSettings();
-            settings.Indent = true;
-            settings.ConformanceLevel = ConformanceLevel.Document;
-            settings.OmitXmlDeclaration = true;
-
-            // This isn't performant, but the whole document has to be rendered
-            // for an accurate data stream
-            string docrender = "";
-            string fragrender = "";
-            using (var sw = new StringWriter())
-            {
-                using (var xw = XmlWriter.Create(sw, settings))
-                {
-                    if (ctx.Node.OwnerDocument is not null)
-                    {
-                        ctx.Node.OwnerDocument.WriteContentTo(xw);
-                    }
-                }
-                docrender = sw.ToString();
-            }
-
-            settings.Indent = false;
-            settings.ConformanceLevel = ConformanceLevel.Fragment;
-            using (var sw = new StringWriter())
-            {
-                using (var xw = XmlWriter.Create(sw, settings))
-                {
-                    ctx.Node.WriteTo(xw);
-                }
-                fragrender = sw.ToString();
-            }
-            string tagname = ctx.Node.Name;
-            string anchor = XmlFragParser.OpeningTagAnchor(tagname).Parse(fragrender);
-            string preamble = $"<{tagname}{anchor}>";
-
-            //string data = FragXmlParser.ChecksumData(preamble, tagname).TryParse(docrender);
-
-            Console.WriteLine("preamble: " + preamble);
-
-            var crc32 = new System.IO.Hashing.Crc32();
-            var bytes = Encoding.UTF8.GetBytes("");
-            crc32.Append(bytes);
-            crc = BitConverter.ToInt32(crc32.GetCurrentHash());
-
             return (double)crc;
         }
 
         public static string text(Context ctx)
         {
             if (ctx.Node is null) return "";
-            return ctx.Node.InnerText;
+            return ctx.Node.Value;
         }
 
         public static string text(Context ctx, string txt)
         {
             if (ctx.Node is null) return "";
-            return ctx.Node.InnerText = txt;
+            ctx.Node.SetValue(txt);
+            return txt;
         }
 
         public static string attr(Context ctx, string name, string value)
         {
-            if (ctx.Node is null || ctx.Node.Attributes is null) return "";
+            if (ctx.Node is null || !ctx.Node.HasAttributes) return "";
-            var attr = ctx.Node.Attributes[name];
+            var attr = ctx.Node.Attribute(name);
             if (attr != null)
             {
                 attr.Value = value;
             }
             else
             {
-                if (ctx.Node.OwnerDocument is null) return "";
+                ctx.Node.SetAttributeValue(name, value);
-                var add = ctx.Node.OwnerDocument.CreateAttribute(name);
-                add.Value = value;
-                ctx.Node.Attributes.SetNamedItem(add);
             }
             return "";
         }
 
         public static string attr(Context ctx, string name)
         {
-            if (ctx.Node?.Attributes?[name]?.Value is string val)
+            var attr = ctx.Node?.Attribute(name);
+            if (attr != null)
             {
-                return val;
+                return attr.Value;
             }
             return "";
         }

Transformation/Rule.cs

@@ -1,5 +1,7 @@
 using System.Collections.Generic;
 using System.Xml;
+using System.Xml.Linq;
+using System.Xml.XPath;
 using XNeedle.Parser.Elements;
 
 namespace XNeedle.Transformation
@@ -9,10 +11,10 @@ namespace XNeedle.Transformation
         public required string XPathSelector { get; set; }
         public required IEnumerable<Part> Body;
 
-        public void Transform(XmlDocument xml)
+        public void Transform(XDocument xml)
         {
             var context = new Context();
-            context.Node = xml.DocumentElement;
+            context.Node = xml.Root;
             Operate(context);
         }
 
@@ -22,12 +24,12 @@ namespace XNeedle.Transformation
             {
                 return;
             }
-            var nodes = ctx.Node.SelectNodes(XPathSelector);
+            var nodes = ctx.Node.XPathSelectElements(XPathSelector);
             if(nodes is null)
             {
                 return;
             }
-            foreach (XmlNode n in nodes)
+            foreach (XElement n in nodes)
             {
                 var loopCtx = ctx.Clone();
                 loopCtx.Node = n;